The present invention relates to bromine-containing 1,2-bis(phenyl)difluoromethanes of the formula: 
wherein x=1-5, and y=0-5. Also disclosed is a method for the preparation of these compounds. The compounds of formula I are useful as intermediates in producing compounds exhibiting pharmaceutical or agricultural activity, and the compounds of formula I are useful as flame retardants.
Decabromodiphenyl alkanes (C1-10), such as decabromodiphenyl methane and decabromodiphenyl ethane are known compounds that are useful as flame retardants, as disclosed in Hussain U.S. Pat. No. 5,008,477. The compounds are prepared by brominating diphenyl alkane, in the presence of a bromination catalyst such as AlCl3 and/or AlBr3, at a temperature of about 50xc2x0 C. to about 60xc2x0 C., wherein the alkane group has 1-10 carbon atoms. It has been found, in accordance with the present invention, that the above-defined bromine-containing 1,2-bis(phenyl)difluoromethylene compounds can be prepared and exhibit improved flame retardancy to flammable materials.
The novel compounds in accordance with the present invention have the general formula 
where:
x is equal to 1-5, y is equal to 0-5; and x=1, y=1 (for o,oxe2x80x2; o,mxe2x80x2; o,pxe2x80x2; m,mxe2x80x2; and m,pxe2x80x2 only). In the case of x=1 and y=0, the para compound is known, but is novel as a flame retardant. Similarly, for x=1, y=1, the para, paraxe2x80x2 compound is known, but is novel as a flame retardant.
The compounds of formula I can be used as synthesis intermediates for the preparation of agricultural and pharmaceutical compounds, and can also be used as flame retardants.
The novel compounds in accordance with the present invention have the general formula: 
where:
x is equal to 1-5, and y is equal to 0-5; and where x=1, and y=0, o and m only (excluding para bromo); and where x=1, and y=1, o,oxe2x80x2; o,mxe2x80x2; o,pxe2x80x2; m,mxe2x80x2; and m,pxe2x80x2 (excluding para, paraxe2x80x2), the excluded compounds are known in the art per se, but not as flame retardants).
The novel compounds are any of the following compounds: 
The compounds of formula I may be prepared in a number of ways. For example, the compounds may be prepared via the reaction of 1,2-bis(phenyl)difluoromethane with a bromination agent, such as elemental bromine in fuming sulfuric acid: 
wherein x=1-5; and y=0-5.
The amount of bromine reacted with the 1,2-bis(phenyl)difluoromethane reactant is readily controlled by adjusting the molar ratio of bromine to 1,2-bis(phenyl)difluoromethane. Excess bromine favors the formation of the more highly brominated compounds of the present invention, whereas lower amounts of bromine favor the production of the less heavily brominated compounds of the present invention.
Alternatively, as is taught in the prior art, different bromination agents may be employed, for example, elemental bromine in the presence of a Lewis acid, or N-bromo compounds such as N-bromosuccinimide and dibromodimethylhydantoin.
The 1,2-bis(phenyl)difluoromethane precursor may be prepared via the reaction of benzophenone with a fluorination agent, such as SF4, diethylaminosulfur trifluoride (DAST), alkylsulfur trifluorides or arylsulfur trifluorides. Alternatively, benzophenone can be transformed to the corresponding hydrazone or 1,3-dithiolane followed by treatment with a fluorination agent such as hydrogen fluoride (HF), polyvinylpyridinium poly(hydrogen fluoride) [PVPPHF], pyridinium poly(hydrogen fluoride) [PPHF], and an N-bromo compound, such as N-bromosuccinimide or dibromdimethyl hydantoin. Preferred is PVPPHF or PPHF and an N-bromo compound, such as N-bromosuccinimide or dibromdimethyl hydantoin. 
All of the above-mentioned compounds are useful as flame retardants for use with any flammable material, as well as the following compounds: 
where
x=0 or 1 and y=0 or 1 and x+y=1-2.
When used as a flame retardant for a flammable material, the bromine-containing 1,2-bis(phenyl)difluoromethane should be incorporated into or onto the flammable material in an amount sufficient to obtain the desired flame retardancy, which varies with the particular flammable material in which the compound(s) is incorporated. In general, the amount of compound(s) incorporated into the flammable material is in the range of about 2% to about 50% by weight of flammable material, preferably about 5% to about 30%, based on the weight of flammable material.
The bromine-containing 1,2-bis(phenyl)difluoromethanes of the present invention are useful for flame retardation of any flammable material, including monomers and oligomers, but are particularly advantageous for flame retarding thermoplastic and thermosetting polymers and copolymers. Examples include polyolefins, polyurethanes, polyamides, polyimides, polycarbonates, polyethers, polyesters, epoxy resins, polyphenols, and elastomers, such as natural rubber, butyl rubber, and polysilanes. The oligomers and polymers may be cross-linked or non cross-linked and may contain typical additives, such as plasticizers, stabilizers, antioxidants, fillers, pigments and the like. The flame retardant compounds of the present invention can be compounded into the flammable material at any stage of processing, e.g., added to the monomer or oligomer prior to, during, or after polymerization, or during extrusion, melt blending, or molding of the flammable material, e.g., polymer.